1. Field of the Invention
This invention refers to a process for the flame retardant treatment of polyamide fabrics or blended fabrics having a substantial polyamide content. The invention also refers to the treating bath and to the fabrics thus treated.
2. Brief Description of the Prior Art
Polyamide fabrics, such as the nylons, have been quite difficult to flame retard. For applications such as curtains, draperies, wall coverings, and upholstery, some degree of wash resistance of the flame retardant finish is desired. Finishes based on thiourea-formaldehyde have been used but these are now recognized as having undesirable toxicological features, odor, and loss of tactile quality. Treatments which consist of applying decabromodiphenyl ether together with antimony oxide and a binder resin are known but these entail costly high add-ons with loss of hand (tactile quality) and undesirable white pigmentation. Most recently, environmental and toxicological concerns have also been raised with respect to decabromodiphenyl ether.
Effective flame retardant finishes for wool are known based on tetrabromophthalic acid and its salts. Tetrabromophthalic anhydride has been applied to wool as well as wool-nylon blends under dyebath conditions was taught by Friedman et al., Textile Res. J. 44 (12), 994-6 (1974), and specifically the use on wool by Friedman et al., U.S. Pat. No. 3,927,962 (1975). The use of tetrabromophthalic anhydride or acid along with potassium hexafluorozirconate is described in a number of publications and patents by Benisek or Benisek et al., exemplified by U.S. Pat. No. 4,447,242 (1984). The use of a finely dispersed tetrabromophthalate salt as a flame retardant treatment for wool is described by Hermann et al. (to Apex Chemical Co.), U.S. Pat. No. 4,277,379 (July 1981) and U.S. Pat. No. 4,302,203 (Nov. 24, 1981), both of which are incorporated herein by reference.
The use of tetrabromophthalic acid or anhydride to flame retard nylon or blends thereof has also been claimed by Alderson, U.S. Pat. No. 3,772,067 (1973) which is referred to without further elaboration by Friedman et al., Textile Research Journal 1974, 44 (12), 994-6. However, such treatments are non-durable to washing, and have found no practical usage. Moreover, the process of Alderson involves the use of an organic carrier, benzyl alcohol, which imposes substantial problems of air and water pollution as well as flammability in handling.
Although applicant has had long experience in applying the Hermann et al. flame retardant to wool and wool-nylon blends with a preponderance of wool, the Hermann et al. flame retardant has not hitherto given effective and durable flame retardant finish on wool-nylon blends of over 20% nylon or on nylon itself.
One probable reason for the poor durability of tetrabromophthalic acid-based finishes on nylon or high nylon wool-nylon blends is that, in contrast to wool which has a fairly high concentration of amino groups along the polyamide chain, synthetic polyamides have only at most one or two amino end groups and offer few sites for binding of tetrabromophthalic acid or its anions.
I have now found surprisingly that by the introduction of a critical amount of an electrolyte into an aqueous solution of an ionizable tetrabromophthalate, substantially free of organic solvent, and at a certain critical pH range, an effective wash-resistant flame retardant treatment of synthetic polyamide fabrics can be achieved. My new process is also effective on blends of synthetic polyamides with wool or other fibers, the process having a major advantage over prior processes when applied to wool-polyamide blends having 20% or more of polyamide.